STCC08 Datasheet, PDF (5/13 Pages) STMicroelectronics – AC switch failure mode detector

STCC08
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Functional description
Functional description
STCC08 functional description
The STCC08 is a power circuit designed to drive up to 10 mA I_GT AC switches and to detect
AC switch failure modes through MCU diagnostic.
It embeds a logic switch driver, an AC switch diode mode detection, a short circuit detection
and an AC switch open detection.
STCC08 can be powered by a 3.3 V or 5 V power supply voltage.
Switch driver
This driver is a logic level buffer (CMOS compatible) interfacing directly with the AC switch
and the microcontroller.
The AC switch must be driven in negative polarity: AC switch COM = A₁ = V_CC
The drive Boolean rule is:
V_in > V_on: switch = ON
V_in < V_on: switch = OFF
The AC switch can be driven in continuous, pulsed or angle phase modes.
In insulated applications, the input can be driven through an opto-coupler powered with a
non-insulated auxiliary power supply.
R_IG pin allows the AC switch gate current to be set. A resistor must be connected between
this pin and the ground GND. This resistor is defined according to the miminmum ambient
temperature and the AC switch I_GT (see Figure 3). This optimizes the consumption of the
application.
Figure 3. R_ig = f(T_{amb_min}) for 5/10 mA AC switches
RIG_Max(Ω)
130
120
AC switch 10 mA @ 25 °C
110
AC switch 5 mA @ 25 °C
100
90
80
70
60
50
40
30
20
10
0
-20 -15 -10
-5
0
5
10
15
20
25
30
Tamb_min (°C)
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